1. Field of the Invention
The present invention relates to a method of annealing a glass product by transferring a glass product of high temperature on a conveyor constituted by a wire mesh belt having gas-permeability in an annealing lehr. In particular, the present invention relates to an annealing apparatus for annealing a glass product, which can minimize a flaw which may occur in the glass product of high temperature due to the contact with a metallic material and a thermal factor when the glass product is placed on a wire mesh belt, or a flaw which may occur by a shock when the glass product is placed on the mesh belt or a flaw which may occur due to a mechanical factor such as fine vibrations when the glass product on the mesh belt is passed in an annealing lehr.
2. Discussion of Background
Generally, a glass product obtained by molding molten glass is annealed to normal temperature or room temperature with use of an annealing lehr so that a stress produced in a cooling step is reduced. In the annealing lehr, a conveyor of a wire mesh belt is used to successively transfer glass products in the annealing lehr. The mesh belt is generally constituted by a wire net formed by weaving a heat-resistant wire of 2.0-4.0 mm in diameter so as to provide a mechanical strength which is durable to the weight of the glass products and a tension during the transferring of the products.
When a glass product of high temperature is placed on such mesh belt, there may cause a flaw in the glass product due to a temperature difference between the wire and the glass product or a flaw in the glass product at the position in contact with the mesh belt due to a mechanical shock when the glass product is brought to contact with the mesh belt. Or there may cause the adhesion of rust on the wire to the contacting surface of the glass product. Further, as a factor of resulting the flaw in the surface of the glass product, it is considered vibrations in the mesh belt which are produced during the transfer of the glass product in the annealing lehr. When such flaw is produced in the glass product, an amount of work to remove the flaw in a polishing process is very large and efficiency of production is reduced. As a method of preventing the occurrence of a flaw in a glass product, there is a method wherein stands for mounting thereon glass products of high temperature are provided on the mesh belt (for example, JP-A-55-32773). In this method, however, a large burden is required to mount and remove the stands when a large number of glass products are successively produced. Namely, in order to conduct the provision and remove of the stands in a mechanical manner, a complicated equipment for providing and removing the stands is required. When such operations are to be conducted manually, a much labor is required.